MERCENARIES QUIT INDIAN OCEAN ISLES

By CHRISTOPHER S. WREN, Special to The New York Times

Published: December 16, 1989

JOHANNESBURG, Dec. 15—
Col. Bob Denard, the French soldier of fortune who ruled the Comoro Islands for the last three weeks, flew to South Africa today with 21 other mercenaries after handing his fief over to the French military authorities.

Colonel Denard, who mounted the coup in 1978 that installed Ahmed Abdallah Abdermane as President and who was accused of having him killed last month, left after a face-saving ceremony with French troops brought in from the island of Mayotte, 180 miles away.

The South African Government made clear that the stay of Colonel Denard and his men would be only temporary and even had airline tickets to Paris awaiting his arrival on a chartered South African Hercules aircraft.

South Africa's Foreign Minister, Roelof F. Botha, told reporters at the airport that the mercenaries had been allowed to come here to ease their withdrawal from the Comoros, a cluster of three volcanic islands in the Mozambique Channel of the Indian Ocean, as part of a settlement worked out with France. He said they would probably leave within 48 hours. No Interviews Allowed

A South African official said earlier that customs officials would inventory the possessions of the mercenaries in the event of claims from either the Comoros or France. He also indicated that they would not be allowed to give interviews to the press while they were in South Africa.

''Why should they stay?'' the official said. ''They're not South African citizens.''

According to reports here, Colonel Denard has a house in Durban, though the South African security police contended that they had no knowledge of it.

Colonel Denard, who took out Comoran citizenship and married a local woman, was reportedly reluctant to return to France, where he faces legal action over his role in an earlier attempt to overthrow the President of Benin more than a decade ago.

He agreed to leave the Comoros, where he has acquired substantial real estate and business interests, after the French Government sent a naval flotilla carrying commandos into the waters off the largest island, Grande Comore. The islands gained independence from France in 1975.

A half-dozen French and Belgian mercenaries, some accompanied by their Comoran families, left for Nairobi and Paris on Thursday on an Air France flight. Controlled Presidential Guard

The mercenaries had controlled the 650-man Presidential Guard, which was the dominant military force on the island. The nominal army was disarmed after President Abdallah's assassination on Nov. 26.

The South African official said Colonel Denard had originally asked for $12 million as the price of his departure. The official said South Africa had refused to pay anything. He said he did not know if any payments had been made by the French Government.

''South Africa has been cooperating with the French Government, and other parties, with a view to insuring the peaceful transfer of power to the civilian authorities in the Comoros,'' Foreign Minister Botha said in a statement read tonight.

''Expatriate elements of the Presidential Guard agreed to leave the islands, and South Africa, in consultation with the French Government and with its approval and at the request of the Comoran authorities, is assisting to provide logistical support in their withdrawal from the islands and return to France,'' he said.